perf daemon: Set control fifo for session

Setup control fifos for session and add --control option to session
arguments.

Example:

  # cat ~/.perfconfig
  [daemon]
  base=/opt/perfdata

  [session-cycles]
  run = -m 10M -e cycles --overwrite --switch-output -a

  [session-sched]
  run = -m 20M -e sched:* --overwrite --switch-output -a

Starting the daemon:

  # perf daemon start

Use can list control fifos with (control and ack files):

  # perf daemon -v
  [776459:daemon] base: /opt/perfdata
    output:  /opt/perfdata/output
    lock:    /opt/perfdata/lock
  [776460:cycles] perf record -m 20M -e cycles --overwrite --switch-output -a
    base:    /opt/perfdata/session-cycles
    output:  /opt/perfdata/session-cycles/output
    control: /opt/perfdata/session-cycles/control
    ack:     /opt/perfdata/session-cycles/ack
  [776461:sched] perf record -m 20M -e sched:* --overwrite --switch-output -a
    base:    /opt/perfdata/session-sched
    output:  /opt/perfdata/session-sched/output
    control: /opt/perfdata/session-sched/control
    ack:     /opt/perfdata/session-sched/ack

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210208200908.1019149-15-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-daemon.txt

@@ -37,6 +37,9 @@ flight recorder sessions in above example or session that is configured
 to produce data periodically, like with --switch-output configuration
 for time and size.
 
+Each session is started with control setup (with perf record --control
+options).
+
 OPTIONS
 -------
 -v::

tools/perf/builtin-daemon.c

@@ -32,6 +32,8 @@
 #include "util.h"
 
 #define SESSION_OUTPUT  "output"
+#define SESSION_CONTROL "control"
+#define SESSION_ACK     "ack"
 
 /*
  * Session states:
@@ -74,6 +76,7 @@ struct daemon_session {
 	char				*base;
 	char				*name;
 	char				*run;
+	char				*control;
 	int				 pid;
 	struct list_head		 list;
 	enum daemon_session_state	 state;
@@ -365,7 +368,18 @@ static int daemon_session__run(struct daemon_session *session,
 	dup2(fd, 2);
 	close(fd);
 
-	scnprintf(buf, sizeof(buf), "%s record %s", daemon->perf, session->run);
+	if (mkfifo(SESSION_CONTROL, O_RDWR) && errno != EEXIST) {
+		perror("failed: create control fifo");
+		return -1;
+	}
+
+	if (mkfifo(SESSION_ACK, O_RDWR) && errno != EEXIST) {
+		perror("failed: create ack fifo");
+		return -1;
+	}
+
+	scnprintf(buf, sizeof(buf), "%s record --control=fifo:%s,%s %s",
+		  daemon->perf, SESSION_CONTROL, SESSION_ACK, session->run);
 
 	argv = argv_split(buf, &argc);
 	if (!argv)
@@ -603,6 +617,12 @@ static int cmd_session_list(struct daemon *daemon, union cmd *cmd, FILE *out)
 				/* session output */
 				csv_sep, session->base, SESSION_OUTPUT);
 
+			fprintf(out, "%c%s/%s%c%s/%s",
+				/* session control */
+				csv_sep, session->base, SESSION_CONTROL,
+				/* session ack */
+				csv_sep, session->base, SESSION_ACK);
+
 			fprintf(out, "\n");
 		} else {
 			fprintf(out, "[%d:%s] perf record %s\n",
@@ -613,6 +633,10 @@ static int cmd_session_list(struct daemon *daemon, union cmd *cmd, FILE *out)
 				session->base);
 			fprintf(out, "  output:  %s/%s\n",
 				session->base, SESSION_OUTPUT);
+			fprintf(out, "  control: %s/%s\n",
+				session->base, SESSION_CONTROL);
+			fprintf(out, "  ack:     %s/%s\n",
+				session->base, SESSION_ACK);
 		}
 	}